Copper (Cu, Latin cuprum) - a chemical element from the group of transition metals of the periodic table. The name of copper in Latin (and behind it also in many other languages, including English) comes from Cyprus, where in the antiquity this metal was mined. Initially, it was called the Cypriot metal (Latin: Aes Cypress), and then Cuprum. It has 26 isotopes from the 55-80 mass range. Two are stable: 63 and 65.

Copper recycling
Copper, just like aluminum is 100% recycled without any loss of quality. In volume, copper is the third most frequently recovered metal after iron and aluminum. It is estimated that 80% of the copper ever extracted is used. Recycling in 2002-2008 provided about 35% of consumed copper. Due to the character of the raw material, it is expected that in the next years the share of recycling in the total copper production will grow.
The process of copper recovery takes place in the same way as in the process of obtaining it, except that it requires fewer steps. High-purity scrap is melted in the furnace, then reduced and poured in the form of billets and bars; low-purity scrap is subjected to electrorefining in a sulfuric acid bath.

Recycling of copper cables is a growing and profitable segment of the secondary waste market.

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Physical properties of copper
Copper puck with a purity of ≥99.95% obtained by continuous casting and etched by surface to show the internal structure

The copper has a density of 8.96 g / cm3 and a melting point of 1084,45 ° C. After melting and cleaning, it is a soft metal with very good thermal and electrical conductivity. Copper, along with silver and gold, lie in the group 11 of the periodic table and have certain common properties: they have one electron in orbital s, valence shells over a full electronic shell d, and are characterized by high plasticity and electrical conductivity. The filled d shells in these elements do not contribute too much to interatomic interactions, which in metallic bonds are dominated by the electrons of the coatings. In contrast to metals with incomplete coatings d, the metallic bond in copper is not covalent and is relatively weak. This explains the low hardness and high plasticity of single copper crystals. Copper can be plastically processed cold and hot, but in the case of cold processing, metal hardening occurs (as a result of crushing), which is removed by recrystallizing annealing (at 400-600 ° C). Hot plastic processing is carried out at 650-800 ° C. On a macroscopic scale, the formation of longitudinal defects of the crystal lattice, such as the boundaries between grains or disturbances of flow under applied force, increases the hardness of copper. For this reason, the copper available commercially is in a finely granular polycrystalline form, having greater mechanical resistance than the monocrystalline form [4].

The low copper hardness partially explains its high electrical conductivity (59,6 × 10 6 S / m) and high thermal conductivity, which is the second largest in clean metals at room temperature. This is due to the fact that the resistance to electron transfer in metals mainly derives from the scattering of electrons on thermal vibrations of the crystal lattice, which are relatively weak in soft metals. The maximum permissible current density for copper in the air is approximately 3.1 × 106 A / m 2 of cross-sectional area, above this value it begins to overheat. As with other metals, if copper is in contact with other metals, galvanic corrosion occurs.
Together with the osmium (bluish), cesium (yellow) and gold (yellow), copper is one of four metals whose natural color is different from gray or silver. Pure copper is orange-red and covers red in the air. The characteristic color of copper comes from the electron transitions between the filled 3d coatings and the semi-solid ones 4s - the energy differences between these coatings correspond to the energy of orange light. The same mechanism is responsible for the yellow color of gold.
Chemical properties of copper

Pure copper contains 0.01-1.0% impurities, depending on the type of preparation, processing and purification. The following elements are considered as impurities: Bi, Pb, Sb, As, Fe, Ni, Sn, Zn and S. It is quite chemically resistant and belongs to semi-precious metals. It is not affected by acids under non-oxidizing conditions, while under oxidative conditions it is dissolved without hydrogen evolution:

3Cu + 8HNO3 (diluted) → 3Cu (NO3) 2 + 2NO ↑ + 4H2O

Cu + 4HNO3 (concentrated) → Cu